silver disc sighted on Waterloo Bridge, London, England in 1983

I was in the back seat of my boyfriends car, my friend was in the front passenger seat and my boyfriend was the driver. We were crossing Waterloo Bridge,London when we were halted by traffic. 
As we sat waiting suddenly to my left a space craft, disk shaped and silver in colour appeared to just drop out of the sky and hovered in front of us to the left of our car. It was huge, hovered in a tilted position, at this point i could see windows all around the craft like portholes, i am sure something was looking out.At the bottom of the craft i noticed a kind of eluminous blue light, like an electric blue colour but softer. I looked to all the people crossing the bridge. It was as though some of the people were frozen. The ones that were frozen were the ones who were pointing up to the craft in amazement. The others appeared not to see the craft at all. These people continued on but appeared slow, it was almost as though time was standing still, like a photo. Suddenly it just vanished. Just shot off and was so fast that it was like magic. I was in shock i looked at my boyfriend and said "Did you see that". He asked me what, he had not seen it, which was amazing as he was the closest to the object. I then looked at my friend and said "Did you see that?" She looked terrified and said "Yes". I told her i was glad she had seen it too as if i told people that i had seen a flying saucer they would think i had  gone mad. But the fact that we had both seen it made me feel more comfortable. My friend refuses to speak about this event to this day she acknowledges that we saw what we saw but doesnt wish to discuss it further.
Witness indicates that date of the incident is approximate.  Witness describes self as a retired public servant.  One of two interesting sightings submitted by same witness.  PD